3 ms·

The estimate is of the kinetic energy and doesn't include thermal energy so I think your derived estimate ends up being circular: https://www.axios.com/nasa-to

by pvg 5y ago

The estimate is of the kinetic energy and doesn't include thermal energy so I think your derived estimate ends up being circular: https://www.axios.com/nasa-tonga-volcano-blast-5-6-megatons-estimate-b7f0a580-7658-4071-a6bd-5e6a3a646eec.html https://www.axios.com/nasa-tonga-volcano-blast-5-6-megatons-... Another difficulty is that you're essentially estimating boiling a blob of water away but that's not what takes place - the process is explosive, quickly dumping lots of 'excess' energy elsewhere. It also doesn't stop heating the water once it hits 100c vapour.

dredmorbius 5y ago
The nature of rough physics back-of-the-envelope (or quick on-the-shell) estimation is to get a rough idea of values and quantities involved. My expectation is that my estimate is somewhere within an order of magnitude of actual values, and suspect it's well on the high side. Modelling the specific events and characteristics of seawater infiltration to magma vents and chambers is well beyond my pay grade. I'm not representing to any extent that I've done this realistically. I'm simply showing what the maximimum potential vaporisation magnitude might be given a 6 MT energy input using a very naive heat of vaporisation conversion. I'd noted the circularity in my note --- I'm estimating vapourisation effects and consequent blast yield using estimations of energy release which are based on the observed blast characteristics. Circular circularity is circularly circular. The Axios article ... provides minimal insight on NASA's estimation methods. Though the comment on kinetic (blast) energies does suggest modeling based on the size, and probably rate of expansion, of the steam and ash plume. A forensic analysis of the 2020 Beiruit explosion discusses how total explosive force is estimated by blast diameter (see: https://forensic-architecture.org/investigation/beirut-port-explosion https://forensic-architecture.org/investigation/beirut-port-...). On thermal vs. blast effects: my estimate is based on the conversion of applied thermal energy into blast energy through vapourisation of water into steam. The 1,000-fold volumetric expansion provides that blast capability. It would then be much of the observed blast that the original 5--6 MT erruption energy is based on. My understanding is that "thermal effects" would refer to additional heat radiated from the erruption, exclusive of that heat which triggered the steam explosion itself.

by pvg 5y ago

dredmorbius 5y ago

The nature of rough physics back-of-the-envelope (or quick on-the-shell) estimation is to get a rough idea of values and quantities involved. My expectation is that my estimate is somewhere within an order of magnitude of actual values, and suspect it's well on the high side. Modelling the specific events and characteristics of seawater infiltration to magma vents and chambers is well beyond my pay grade. I'm not representing to any extent that I've done this realistically. I'm simply showing what the maximimum potential vaporisation magnitude might be given a 6 MT energy input using a very naive heat of vaporisation conversion. I'd noted the circularity in my note --- I'm estimating vapourisation effects and consequent blast yield using estimations of energy release which are based on the observed blast characteristics. Circular circularity is circularly circular. The Axios article ... provides minimal insight on NASA's estimation methods. Though the comment on kinetic (blast) energies does suggest modeling based on the size, and probably rate of expansion, of the steam and ash plume. A forensic analysis of the 2020 Beiruit explosion discusses how total explosive force is estimated by blast diameter (see: https://forensic-architecture.org/investigation/beirut-port-explosion https://forensic-architecture.org/investigation/beirut-port-...). On thermal vs. blast effects: my estimate is based on the conversion of applied thermal energy into blast energy through vapourisation of water into steam. The 1,000-fold volumetric expansion provides that blast capability. It would then be much of the observed blast that the original 5--6 MT erruption energy is based on. My understanding is that "thermal effects" would refer to additional heat radiated from the erruption, exclusive of that heat which triggered the steam explosion itself.